Flexible printed board

Abstract

To provide a flexible printed board that is less prone to peeling of an adhesive layer even when held in a high temperature environment for a long period of time, compared to a conventional flexible printed board.SOLUTION: A flexible printed board 100 has at least a substrate layer 110, an adhesive layer 120, a nickel-containing layer 130, and a conductor 140 in that order, the adhesive layer contains fluorine-containing rubber, the mass per unit area of nickel in the nickel-containing layer is 100 mg / m2 or more, and the substrate layer contains polyimide.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a flexible printed circuit board.

Background Art

[0002] Flexible printed circuit boards are widely used as substrates for various electronic devices, and in recent years, long-term use in high-temperature environments such as near the semiconductors of inverters has been considered (see Patent Document 1). A general flexible printed circuit board has a long-term heat-resistant temperature of about 80°C. When used in an environment as described above, the adhesive layer provided between the base material layer and the conductor forming the circuit pattern becomes brittle,

[0003] and problems such as peeling between the base material layer and the conductor are a concern. In a general flexible printed circuit board, in the above adhesive layer, an epoxy resin or an acrylic resin is mainly used as a main component, but it is not suitable for use in a long-term high-temperature environment, and delamination between layers occurs. For this reason, development using an adhesive containing fluorine-containing rubber has also been promoted. For example, Patent Document 2 discloses a technique related to a flexible printed circuit board in which long-term heat resistance of 1000 hours is achieved by using an adhesive having a high thermal decomposition temperature containing a fluorine-based rubber and a film having low oxygen permeability in a high-temperature environment.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] The adhesive layer containing fluorine-based rubber provided on the flexible printed circuit board of Patent Document 2 was found to be able to maintain heat resistance for about 1000 hours. However, in a long-term high-temperature environment of 3000 hours required for actual automotive parts, the adhesive layer gradually peels off from the end of the substrate, resulting in usage environment and design limitations.

[0006] In view of such problems, an object of the present invention is to provide a flexible printed circuit board in which peeling of the adhesive layer is less likely to occur even when held in a high-temperature environment for a long time as compared with a conventional flexible printed circuit board.

Means for Solving the Problems

[0007] As a result of intensive studies, the present inventors have found that the above problems can be solved by providing a layer containing a specific amount of nickel between the adhesive layer containing fluorine-containing rubber and the conductor, and have reached the present invention.

[0008] That is, the present invention is as follows. [1] Having at least a base material layer, an adhesive layer, a nickel-containing layer, and a conductor in this order, The adhesive layer contains fluorine-containing rubber, The mass per unit area of nickel in the nickel-containing layer is 100 mg / m 2 or more, a flexible printed circuit board. [2] The flexible printed circuit board according to [1], wherein the base material layer contains polyimide. [3] The flexible printed circuit board according to [1] or [2], wherein the mass per unit area of nickel in the nickel-containing layer is 125 mg / m 2 or more and 500 mg / m 2 or less. [4] The flexible printed circuit board according to any one of [1] to [3], wherein the conductor contains copper. [5] A lamination step of obtaining a laminate including at least a base material layer, an adhesive layer, a nickel-containing layer, and a conductor layer in this order, and The method for manufacturing a flexible printed circuit board has a circuit pattern forming step of processing the laminate so that a circuit pattern is formed. The adhesive layer contains a fluorine-containing rubber. The mass per unit area of nickel in the nickel-containing layer is 100 mg / m 2 or more. Method for manufacturing a flexible printed circuit board. [6] The method for manufacturing a flexible printed circuit board according to [5], wherein the laminating step includes a step of bonding the base material layer and the laminate layer including the nickel-containing layer and the conductor layer with an adhesive. [Advantages of the Invention]

[0009] According to the present invention, it is possible to provide a flexible printed circuit board in which peeling of the adhesive layer is less likely to occur even when it is held in a high-temperature environment for a long time, as compared with a conventional flexible printed circuit board. [Brief Description of the Drawings]

[0010]

Figure 1

Figure 2

[0011] Hereinafter, embodiments of the present invention will be described in detail. However, these descriptions are examples (representative examples) of the embodiments of the present invention, and the present invention is not limited to these contents as long as the gist thereof is not exceeded. In this specification, a numerical range represented by "~" means a range including the numerical values described before and after "~" as the lower limit value and the upper limit value, and "A~B" means A or more and B or less. In addition, although a plurality of embodiments are described in this specification, various conditions in each embodiment can be applied to each other within the applicable range. In addition, the drawings of the present application are schematically illustrated to facilitate understanding of the features of the embodiments, and the dimensional ratios of each component are not necessarily the same as the actual ones.

[0012] <Flexible printed circuit board> A flexible printed circuit board (hereinafter, also simply referred to as "flexible printed circuit board") according to an embodiment of the present invention has at least a base material layer, an adhesive layer, a nickel-containing layer, and a conductor in this order, the adhesive layer contains a fluorine-containing rubber, and the mass per unit area of nickel in the nickel-containing layer is 100 mg / m 2 or more, and it is a flexible printed circuit board.

[0013] In a general flexible printed circuit board, peeling of the adhesive easily occurs between the adhesive layer and the conductor. For example, in a high-temperature environment, copper generally used as a conductor material may promote the thermal decomposition reaction (low molecular weight) of the fluorine-containing rubber in the adhesive layer, and as a result, peeling of the adhesive occurs. On the other hand, the above flexible printed circuit board provides a nickel-containing layer having a specific nickel content between the adhesive layer and the conductor, thereby suppressing the reaction between a metal that can be used for a conductor such as copper and the fluorine-containing rubber in the adhesive layer, and suppressing the deterioration of the adhesive and thus the peeling of the adhesive layer over a long period at high temperature, particularly for a period of 3000 hours or more, which is required for actual automotive parts. Regarding the reaction between a metal that can be used for a conductor such as copper and the fluorine-containing rubber in the adhesive layer, it is disclosed in "Yoshito Ohtake, 'Deterioration, Troubles, and Countermeasures of Elastomer Products (Deterioration by Residual Chlorine Water, Metal Deterioration, and Ozone Deterioration due to Global Environmental Deterioration)', Journal of the Rubber Society of Japan, Vol. 79, No. 19, 2006, pp. 529-536" that fluorine rubber undergoes thermal oxidative deterioration by copper.

[0014] ​An example of the flexible printed circuit board according to this embodiment is shown in FIG. 1. The flexible printed circuit board 100 shown in FIG. 1 is a flexible printed circuit board having a base material layer 110, an adhesive layer 120, a nickel-containing layer 130, and a conductor 140 for forming a circuit pattern in this order. The flexible printed circuit board 100 according to this embodiment only needs to have at least the above-described components, and may have other layers. In FIG. 1, the depiction of the conductor forming the circuit pattern is omitted. Hereinafter, each component constituting the flexible printed circuit board 100 will be described.

[0015] [Base Material Layer] The average thickness of the base material layer 110 is not particularly limited, but is preferably 12.5 μm or more and 125 μm or less, and more preferably 25 μm or more and 75 μm or less. In this specification, the "average thickness" means the average value of the thicknesses measured at a plurality of locations of the target substance.

[0016] The material of the base material layer 110 is not particularly limited. For example, as the base material layer 110, a layer made of a resin film such as a polyimide film or a liquid crystal polymer film can be used. Further, the resin film layer can be a layer containing at least one selected from the group consisting of a polyimide film and a liquid crystal polymer. The base material layer 110 may be made of one kind of film, or may be a film in which two or more kinds of films are laminated. Further, a metal vapor deposition film in which a metal such as aluminum is vapor deposited on a resin film can also be used as the resin film layer. Specifically, as the base material layer 110, UPILEX series (polyimide film manufactured by Ube Industries), VECTOR series (liquid crystal polymer manufactured by Kuraray), etc. can be used. When using a liquid crystal polymer of the VECTOR series as the resin film layer, among the VECTOR series, VECTOR CTF is preferable from the viewpoint of oxygen permeability.

[0017] From the perspective of improving heat resistance, the base material layer 110 preferably contains polyimide and is preferably a polyimide film. When a polyimide film is used as the base material layer 110, the polyimide film preferably contains polyimide which is a polymer of a tetracarboxylic acid component and a diamine component. The tetracarboxylic acid component is not particularly limited, but is preferably at least one selected from the group consisting of biphenyltetracarboxylic acids such as 3,3',4,4'-biphenyltetracarboxylic acid, pyromellitic acid, and acid anhydrides thereof and esterified products of these acids with lower alcohols. The tetracarboxylic acid component more preferably contains 3,3',4,4'-biphenyltetracarboxylic acid, and even more preferably contains 3,3',4,4'-biphenyltetracarboxylic dianhydride. The diamine component is not particularly limited, but is preferably at least one selected from the group consisting of 1,4-phenylenediamine, 1,3-phenylenediamine, 1,2-phenylenediamine, 2,4-diaminotoluene, 2,5-diaminotoluene, and 2,6-diaminotoluene.

[0018] More preferably, the polyimide film contains polyimide which is a polymer of monomers containing at least one selected from the group consisting of 1,2-phenylenediamine, 1,3-phenylenediamine, and 1,4-phenylenediamine and at least 3,3',4,4'-biphenyltetracarboxylic dianhydride. Even more preferably, it contains polyimide which is a polymer of monomers containing at least 1,4-phenylenediamine and 3,3',4,4'-biphenyltetracarboxylic dianhydride. When the polyimide film contains the above polyimide, it is preferable because the unit structures of the polyimide overlap with each other to form a structure that is less permeable to oxygen. Specific examples of the polyimide film corresponding to a polymer of monomers containing at least 1,4-phenylenediamine and 3,3',4,4'-biphenyltetracarboxylic dianhydride include UPILEX-S.

[0019] The oxygen transmission rate of the base material layer 110 is usually 1.50×10 -10 cc·cm / cm 2 ·sec·cmHg or less, preferably 1.00×10 -10 cc·cm / cm 2 ·sec·cmHg or less, more preferably 1.00×10 -11 cc·cm / cm 2 ·sec·cmHg or less. The lower limit value of the oxygen transmission rate is not particularly limited, and the lower the better. For example, it can be 1.00×10 -15 cc·cm / cm 2 ·sec·cmHg or more can be. Further, the range of the oxygen transmission rate is preferably satisfied by the oxygen transmission rate at 200°C. When the above oxygen transmission rate is below the above upper limit, the oxidative degradation of the conductor in a high-temperature environment is suppressed, and it becomes easier to prevent the decrease in the peel strength of the base material layer 110. The oxygen transmission rate can be controlled by the monomer components constituting the resin film. Further, the oxygen transmission rate can also be controlled by coating the resin film with an organic layer or an inorganic layer, adhering an organic film or an inorganic film to the resin film, or adding an organic filler or an inorganic filler to the resin film.

[0020] The oxygen transmission rate of the base material layer 110 can be measured under the following conditions. Measurement method: Conform to Appendix 2 of JIS K7126-1 Test gas type: Oxygen Test gas flow rate: 90 ml / min Carrier gas type: Helium Carrier gas flow rate: 35 ml / min Permeation area: 15.2 cm 2 Measuring device: GTR-10AH (200°C) or GTR-30XANO (~120°C), both manufactured by GTR Tech Cell thermostat temperature: 25°C, 120°C, 200°C Gas chromatograph calibration method: Two-point calibration with 0.0 μl and 15.3 μl

[0021] [Adhesive layer] The average thickness of the adhesive layer 120 is not particularly limited. From the viewpoint of adhesiveness, it is preferably 5 μm or more, more preferably 10 μm or more from the viewpoint of embedding the roughness of the conductor, and preferably 30 μm or less from the viewpoint of the processability of the flexible printed circuit board. Usually, when the thickness is 10 μm or more, the adhesive strength does not change even if the thickness is increased.

[0022] The adhesive layer 120 may be a cured product of an adhesive. Hereinafter, the conditions of the adhesive will be described, and the conditions of the adhesive may be treated as the conditions of the adhesive layer 120 within an applicable range. For example, "the content of the fluorine-containing rubber in the adhesive" can be treated as "the content of the fluorine-containing rubber in the adhesive layer".

[0023] The adhesive is not particularly limited as long as it contains a fluorine-containing rubber, and known adhesives can be used. The fluorine-containing rubber may or may not have an unsaturated bond, but it is more preferably to have an unsaturated bond. The fluorine-containing rubber having an unsaturated bond can be obtained by introducing an unsaturated bond into the fluorine-containing rubber by a known method. For example, a method by base modification such as alkali modification can be mentioned.

[0024] The material of the adhesive layer 120 is not particularly limited as long as it contains a fluorine-containing rubber from the viewpoint of heat resistance, but it may have other components. The reason why the heat resistance is improved when the adhesive contains a fluorine-containing rubber is speculated by the present inventors as follows. The binding energy between carbon and fluorine (C-F bond) is known to be greater than the binding energy between carbon and hydrogen (C-H bond). Therefore, by modifying rubber with fluorine to increase the C-F bond, it is possible to make it difficult for the elemental bond to be broken by heat. Also, focusing on the ease of rotation of the carbon-carbon (C-C) bond in the main chain of the resin, the case where fluorine modification is performed (i.e., the case of -CF2-) is less likely to rotate and has a greater binding energy than the case where fluorine modification is not performed (i.e., the case of -CH2-). Therefore, thermal decomposition is less likely to occur and the heat resistance is improved. Furthermore, when the fluorine-containing rubber has an unsaturated bond, since the unsaturated bond can react with the thermosetting resin described later, the heat resistance is further improved.

[0025] Examples of the fluorine-containing rubber include polymers or copolymers of at least one monomer selected from the group consisting of vinyl fluoride, vinylidene fluoride, hexafluoropropene, and tetrafluoroethylene. More preferably, it is a copolymer of at least one monomer selected from the group consisting of vinylidene fluoride, hexafluoropropene, and tetrafluoroethylene. The copolymer is preferably a binary copolymer or a terpolymer, and more preferably a binary copolymer. Examples of the fluorine-containing rubber having an unsaturated bond include unsaturated bond-introduced products of the above polymers or copolymers. In the copolymer, fluorinated olefins such as ethylene, propylene, alkyl vinyl ether, hexafluoroisobutene, vinyl acetate, olefins, vinyl compounds, etc. may be copolymerized to such an extent that the effects of the present disclosure are not impaired. Specifically, for example, polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinyl fluoride, polyvinylidene fluoride, vinylidene fluoride-hexafluoropropene copolymer, tetrafluoroethylene-hexafluoropropene copolymer, chlorofluoroethylene-vinylidene fluoride copolymer, and unsaturated bond-introduced products thereof, etc. may be mentioned. Preferably, it is a vinylidene fluoride - hexafluoropropene copolymer and an unsaturated - bond - introduced product of the copolymer, and more preferably an unsaturated - bond - introduced product of a vinylidene fluoride - hexafluoropropene copolymer. The copolymerization ratio (vinylidene fluoride: hexafluoropropene) is preferably 3:7 to 9.5:0.5, and more preferably 5:5 to 9:1 on a mass basis. The fluorine - containing rubber may be used alone or in combination of two or more. Also, a fluorine - containing rubber having no unsaturated bond and a fluorine - containing rubber having an unsaturated bond may be used in combination.

[0026] The Mooney viscosity (ML 1+10 (121 °C)) of the fluorine - containing rubber or the fluorine - containing rubber having an unsaturated bond is preferably 40 to 110. When it is in the above range, the sheet - processing property is excellent, and the elastic modulus and elongation rate are in an appropriate range, so the punching - processing property, the adhesive strength at high temperature, the solder heat resistance, the adhesive strength after a durability test at high temperature for a long time, and the processing property in the B - stage state are good. The Mooney viscosity (ML 1+10 (121 °C)) is more preferably 50 to 100. The Mooney viscosity can be controlled by factors such as the molecular weight of the material. For example, the Mooney viscosity can be increased by increasing the molecular weight. The measurement of the Mooney viscosity is carried out in accordance with JIS K 6300 - 1(2013). Using a Mooney viscometer SMV - 201 (manufactured by Shimadzu Corporation), the viscosity is measured at a temperature condition of 121 °C, with a pre - heating time of 1 minute and a rotor rotation time of 10 minutes.

[0027] These polymers or copolymers can be subjected to a dehydrofluorination reaction in the presence of a ketone - based solvent such as acetone or methyl ethyl ketone, if necessary, with an alkaline substance such as potassium hydroxide, sodium hydroxide, cesium hydroxide, calcium hydroxide, calcium carbonate, or triethylamine, preferably at a temperature of about 2 to 70 °C, to form an unsaturated bond in the molecule. In the fluorine-containing rubber having an unsaturated bond, the content of the unsaturated bond (content of -CH=CH-) is preferably 0.1% by mass to 30% by mass, more preferably 0.5% by mass to 10% by mass. As the fluorine-containing rubber and the fluorine-containing rubber having an unsaturated bond, commercially available products can also be used.

[0028] The content of the fluorine-containing rubber in the adhesive is not particularly limited. For example, it may be 40% by mass or more, and may also be 80% by mass or less.

[0029] The adhesive may contain a rubber other than the fluorine-containing rubber as long as the effects of the present invention can be obtained.

[0030] (Thermosetting resin) The adhesive may be in the form of an adhesive composition. The adhesive composition can contain a thermosetting resin. The thermosetting resin preferably has a softening point of 30°C or higher. That is, it is preferably in a solid state at room temperature (25°C). The softening point is more preferably 30°C to 160°C, still more preferably 40°C to 160°C, even more preferably 50°C to 150°C, and particularly preferably 60°C to 130°C. In the manufacturing process of a printed wiring board such as a flexible printed circuit board, in the B-stage (semi-cured) state before hot pressing, processing such as drilling for component mounting may be required. By using a thermosetting resin having a softening point within the above range and being in a solid state at room temperature, effects such as good miscibility between the fluorine-containing rubber and other rubbers and improvement in the elastic modulus of the inorganic filler described later can be obtained, and the processability in the B-stage state becomes even better. The softening point of the resin can be measured by the ring and ball method of JIS K 7234. For the measuring device, for example, a METTLER softening point measuring device (FP900 thermosystem) manufactured by METTLER TOLEDO can be used.

[0031] The thermosetting resin is preferably either a phenol resin, an epoxy resin, or a mixture of two or more of these from the viewpoints of reactivity and heat resistance. Examples of the epoxy resin include bisphenol type epoxy resins such as bisphenol A type epoxy resin, bisphenol F type epoxy resin, and bisphenol S type epoxy resin; novolak type epoxy resins such as phenol novolak type epoxy resin, cresol novolak type epoxy resin, and bisphenol A novolak type epoxy resin; alicyclic epoxy resin; aliphatic chain epoxy resin; diglycidyl ether compound of biphenol; diglycidyl ether compound of naphthalene diol; diglycidyl ether compound of phenols; diglycidyl ether compound of alcohols; or their alkyl-substituted products or hydrogenated products. The epoxy resin may be used alone or in combination of two or more.

[0032] The phenolic resin is obtained by reacting phenols and aldehydes with an acid or an alkali as a catalyst. Examples of the phenols include phenol, m-cresol, p-cresol, o-cresol, isopropylphenol, and nonylphenol. Examples of the aldehydes include formaldehyde, paraformaldehyde, acetaldehyde, paraacetaldehyde, butyraldehyde, octylaldehyde, and benzaldehyde. Generally, formaldehyde or paraformaldehyde is used. In addition, vegetable oil-modified phenolic resin can also be used. The vegetable oil-modified phenolic resin is obtained by reacting phenols and vegetable oil in the presence of an acid catalyst and then reacting aldehydes in the presence of an alkali catalyst. Examples of the acid catalyst include p-toluenesulfonic acid. Examples of the alkali catalyst include amine-based catalysts such as ammonia, trimethylamine, and triethylamine. In addition, as the thermosetting resin, xylene resin, guanamine resin, diallyl phthalate resin, vinyl ester resin, unsaturated polyester resin, furan resin, polyimide resin, polyurethane resin, cyanate resin, maleimide resin, or benzocyclobutene resin can also be used.

[0033] The thermosetting resin preferably contains an epoxy resin, and is preferably an epoxy resin. The epoxy resin is preferably a cresol novolak type epoxy resin, and more preferably an o-cresol novolak type epoxy resin. Such an epoxy resin may be a commercially available one, for example, YDCN700-10 (Nippon Steel & Sumikin Chemical Co., Ltd.), N695 (DIC Corporation), etc. The content of the thermosetting resin is preferably 8 to 120 parts by mass with respect to 100 parts by mass of the fluorine-containing rubber. When it is within the above range, the punching processability and the adhesive strength at high temperature are improved. The content is more preferably 8 to 110 parts by mass, and still more preferably 8 to 100 parts by mass.

[0034] (Inorganic filler) The adhesive composition can contain an inorganic filler. Known materials can be used for the inorganic filler. The inorganic filler is preferably electrically insulating. For example, silica, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, calcium silicate, aluminum silicate, calcium carbonate, aluminum oxide, magnesium oxide, antimony oxide, tin oxide, titanium oxide, manganese oxide, zirconium oxide, silicon nitride, aluminum nitride, boron nitride, talc, mica, or kaolin, etc. can be mentioned.

[0035] Since the fluorine-containing rubber has a low elastic modulus, during processing in the B-stage state, generation of burrs of the adhesive and adhesion of the adhesive to the processed part may occur. On the other hand, by using an inorganic filler in the adhesive composition, the elastic modulus can be improved and the processability becomes good. The inorganic filler preferably has thixotropy that can aggregate to some extent and easily increase the elastic modulus. From such a viewpoint, silica, aluminum hydroxide, talc, etc. are preferable. More preferably, it is silica. Silica can be used without particular limitation such as dry silica or wet silica. Commercially available silica can also be used. For example, Aerosil 200 (Nippon Aerosil Co., Ltd.) etc. can be mentioned.

[0036] The inorganic filler may be hydrophobically treated. Examples of the hydrophobization treatment include silicone oil treatment and silane coupling agent treatment. The number average particle diameter of the primary particles of the inorganic filler is preferably 10 nm to 100,000 nm, more preferably about 50 nm to 10,000 nm. The content of the inorganic filler is preferably 1 part by mass to 3 5 parts by mass, more preferably 1 part by mass to 30 parts by mass, and still more preferably 3 parts by mass to 25 parts by mass with respect to 100 parts by mass of the fluorine-containing rubber. By being in the above range, in addition to processability, adhesiveness, solder heat resistance, and durability at high temperature for a long time are improved.

[0037] (amine compound) The adhesive composition may contain an amine compound as a curing agent. As the curing agent for the epoxy resin which is a thermosetting resin, dicyandiamide having a low curing start temperature and excellent stability at room temperature is preferable, and an imidazole compound may be used as a curing aid as necessary. Further, as the curing agent for the fluorine-containing rubber having an unsaturated bond, from the viewpoint of curability, an aromatic diamine compound is preferable as the amine compound. Examples of the aromatic diamine compound include those represented by the following formula (I).

[0038]

Chemical formula

[0039] In formula (I), R 1 , R 2 are each independently an alkyl group having 1 to 6 carbon atoms, and R 3 is at least one selected from the group consisting of an alkylene group having 1 to 6 carbon atoms, an aromatic hydrocarbon group, a carbonyl group, a fluorene group, a sulfonyl group, an ether group, and a sulfide group, and m and n are each independently an integer of 0 to 4. The alkyl group is preferably a methyl group, an ethyl group, or a propyl group. From the viewpoint of curability, a methyl group or an ethyl group is more preferable. The alkylene group is preferably a methylene group or an ethylene group. From the viewpoint of curability, a methylene group is more preferable.

[0040] From the viewpoints of storage stability and excellent rapid curability, m and n are each independently preferably an integer of 0 to 2, more preferably 1 or 2, and even more preferably 2. In formula (I), the arrangement of -NH2 is preferably para to R 3 from the viewpoint of curability. The aromatic hydrocarbon group is not particularly limited as long as it is divalent. For example, phenylene can be mentioned. The aromatic hydrocarbon group can have a substituent such as a methyl group.

[0041] R 3 may be a substituent in which an aromatic hydrocarbon group and an alkylene group are combined, and the combination of the aromatic hydrocarbon and the alkylene group is not particularly limited. For example, an alkylene group having an aromatic hydrocarbon group can be mentioned. Specifically, for example, a mode in which two alkylene groups are bonded via an aromatic hydrocarbon, a mode in which an aromatic hydrocarbon is bonded as a side chain of an alkylene group, and a mode in which an aromatic hydrocarbon group and an alkylene group are bonded and the aromatic hydrocarbon group and the alkylene group are each bonded to two benzene rings shown in formula (I) can be mentioned. Examples of the aromatic hydrocarbon include a benzene ring and naphthalene. The aromatic hydrocarbon can have a substituent such as a methyl group. Among the compounds represented by formula (I), 4,4'-methylenebis(2-ethyl-6-methylaniline) is particularly preferable. The content of the amine compound is preferably 0.1 part by mass to 20 parts by mass, more preferably 1 part by mass to 10 parts by mass, based on 100 parts by mass of the fluorine-containing rubber. Also, a preferable embodiment is that the content of the amine compound is 0.5 part by mass to 30 parts by mass based on 100 parts by mass of the epoxy resin. ​

[0042] (Adhesive composition) The above adhesive composition can be obtained by mixing a fluorine-containing rubber and, if necessary, other additives such as a thermosetting resin, an inorganic filler, and a curing agent. When mixing, an organic solvent may be used if necessary. The above adhesive or adhesive composition is preferably for use in the production of flexible printed boards. For example, an adhesive film using the adhesive or adhesive composition can be obtained and used in the production of flexible printed boards.

[0043] The elastic modulus of the adhesive layer (or the elastic modulus when the adhesive composition is in the B-stage state (semi-cured state)), measured in accordance with the test method for tensile properties of JIS K 7127, is preferably 15 MPa or more. More preferably, it is 20 MPa or more. The upper limit is not particularly limited, but is preferably 3000 MPa or less, more preferably 1000 MPa or less, and still more preferably 100 MPa or less. Also, the elongation at break of the adhesive layer (or the elongation at break when the adhesive composition is in the B-stage state (semi-cured state)), measured in accordance with the test method for tensile properties of JIS K 7127 (1999), is preferably less than 400%. More preferably, it is less than 300%, and still more preferably less than 200%. The lower limit is not particularly limited, but is preferably 50% or more, more preferably 100% or more. When the elastic modulus and the elongation at break are within the above ranges, the processability is improved. The elastic modulus and the elongation at break can be controlled by the softening point of the thermosetting resin, the Mooney viscosity of the fluorine-containing rubber, the content of the inorganic filler, etc.

[0044] The adhesive layer 120 can be manufactured by a known method. For example, an organic solvent solution of the above adhesive composition is prepared and applied to a resin film layer such as polyimide to form a pre-adhesive layer. Then, it is dried under conditions such as 50°C to 160°C for 1 minute to 15 minutes to bring the pre-adhesive layer into a B-stage state, and the adhesive layer 120 is obtained. Thereafter, the obtained adhesive layer 120 can be bonded to an adherend and heat-cured. In the production of the flexible printed circuit board 100, when the above adhesive composition is used for adhesion of a coating layer or the like, adhesion can be performed in the same manner to obtain a flexible printed circuit board 100 having an adhesive layer containing a cured product of the adhesive composition. During the period from the B-stage state to heat curing, if necessary, drilling or the like can also be performed.

[0045] The method for obtaining the adhesive composition in the B-stage state is not particularly limited, and a known method can be adopted, including the method of heat-drying as described above. The organic solvent is not particularly limited, and known ones can be used. For example, acetone, methyl ethyl ketone, tetrahydrofuran, chloroform, dimethylformamide, or methyl isobutyl ketone, etc. can be mentioned. The amount of the organic solvent used is not particularly limited, but it may be used in a range where the solid content contained is preferably 10% by mass to 70% by mass, more preferably 20% by mass to 40% by mass.

[0046] The 3% heat mass loss temperature of the adhesive is preferably 320°C or higher, more preferably 350°C or higher, and even more preferably 370°C or higher. The upper limit value of the 3% heat mass loss temperature is not particularly limited, but from the viewpoint of laser processability, it is preferably 600°C or lower. The 3% heat mass loss temperature can be controlled by optimizing the molecular structure, crosslink density, etc. and the like.

[0047] As the adhesive layer 120, those in which two or more resins are laminated can also be used. When two or more layers are laminated as the adhesive layer 120, the laminate is treated as one adhesive layer.

[0048] [Nickel-containing layer] The nickel-containing layer 130 has no particular limitation as long as the mass per unit area of nickel in the layer is 100 mg / m 2 or more. By providing this layer between the adhesive layer 120 and the conductor 140, it is possible to suppress the deterioration of the adhesive under high temperature for a long period of time, and thus suppress the peeling of the adhesive layer 120. The mass per unit area of nickel in the nickel-containing layer is preferably 100 mg / m 2 or more, but preferably 125 mg / m 2 or more and 500 mg / m 2 or less. By setting it to be not less than the lower limit of this range, a sufficient peeling suppression effect can be obtained. Also, by setting it to be not more than the upper limit of this range, the manufacturing of the substrate becomes advantageous. For example, the etching process for forming wiring becomes easier. The average thickness of the nickel-containing layer 130 has no particular limitation. For example, it may be 110 Å or more, and may also be 570 Å or less. This average thickness can be calculated from the area of the nickel-containing layer, the amount of components in the nickel-containing layer, and the specific gravity.

[0049] The nickel content in the nickel-containing layer 130 can be measured by the following method. First, a first mixed solution mixed with hydrochloric acid:nitric acid = 3:1 (volume ratio) and a second mixed solution mixed with water:aqua regia = 3:2 (volume ratio) (mixed by adding aqua regia to water) are obtained. The laminate of the conductor (conductor layer) 140 and the nickel-containing layer 130 in the flexible printed circuit board 100 is immersed in the second mixed solution for extraction, and ICP emission spectrometry is performed using the obtained extract to determine the amount of nickel. Finally, the nickel content in the nickel-containing layer 130 can be calculated from the obtained amount of nickel and the mass of the nickel-containing layer 130. Further, when it is difficult to remove the nickel-containing layer 130 from the flexible printed circuit board 100, the flexible printed circuit board 100 or a part thereof is immersed in a solvent in which the nickel-containing layer 130 dissolves, and it can be evaluated by performing ICP emission spectrometry on the obtained solution. Note that the object to be immersed in the second mixed solution (the object of extraction) is preferably the laminate of the conductor 140 and the nickel-containing layer 130 in the flexible printed circuit board 100 as described above, but the flexible printed circuit board 100 may also be used. The mass per unit area of nickel in the nickel-containing layer can be obtained by dividing the nickel content in the nickel-containing layer by the area in the planar direction of the nickel-containing layer.

[0050] Components other than nickel constituting the nickel-containing layer 130 are not particularly limited, and examples thereof include Co, Mo, Zn, or Cr.

[0051] [Conductor] There is no particular limitation on the conductor 140, and known materials can be used. For example, copper, silver, gold, tin, aluminum, or indium, or alloys thereof can be mentioned. The conductor 140 is preferably a material containing copper, and more preferably a copper foil. The average thickness of the conductor 140 is not particularly limited, but is preferably 5 μm or more and 500 μm or less, and more preferably 12 μm or more and 500 μm or less. The circuit pattern formed by the conductor 140 is not particularly limited and can be appropriately designed according to the application.

[0052] [Other Layers] The flexible printed circuit board 100 may have layers other than the above-described base material layer 110, adhesive layer 120, nickel containing layer 130, and conductor 140 (other layers).

[0053] [Peel Strength] The peel strength of the conductor with respect to the base material layer is not particularly limited, but is preferably 0.49 N / mm or more in accordance with the JPCA standard JPCA-DG02-2006, and from the viewpoint of achieving the strength required when used as automotive parts, it is preferably the peel strength after 3000 hours at 225 °C. The peel strength can be evaluated in accordance with IPC TM650 2.4.9 (Free Wheeling Rotary Drum Method).

[0054] [Method for Manufacturing Flexible Printed Circuit Board] The method for manufacturing the above-described flexible printed circuit board 100 is not particularly limited, and it can be manufactured using a known method or a combination of known methods. The method for manufacturing the flexible printed circuit board 100 is, for example, a lamination step of obtaining a laminate including at least a base material layer, an adhesive layer, a nickel-containing layer, and a conductor layer in this order, and a circuit pattern forming step of processing the laminate so that a circuit pattern is formed, wherein the adhesive layer contains a fluorine-containing rubber, and the mass per unit area of nickel in the nickel-containing layer is 100 mg / m 2 or more, which may be a method for manufacturing a flexible printed circuit board. In particular, the lamination step preferably includes a step of adhering the base material layer and a laminate layer including the nickel-containing layer and the conductor layer with an adhesive.

[0055] The method for forming the nickel-containing layer is not particularly limited. For example, a method of plating nickel on the surface of a conductor can be mentioned, and known methods such as wet plating or dry plating can be applied. Specifically, methods such as electrolytic plating, electroless plating, vacuum evaporation, or sputtering can be applied.

[0056] <Uses of the flexible printed circuit board> The uses of the above-described flexible printed circuit board 100 are not particularly limited. For example, it can be used as a board mounted on an automobile, a printed wiring board, a liquid crystal display, a robot, a television, a car navigation system, a game machine, a mobile phone, a digital camera, a personal computer, a printer, a light-emitting diode lighting, or a wearable device, etc. Among these, from the viewpoint of being held at a high temperature for a long period of time, it is preferably used as a member (component) for an automobile.

[0057] The usage mode of the flexible printed circuit board 100 is not particularly limited, but it can be used as a board provided in a power module. The mode of the power module is not particularly limited. For example, a board, a SiC semiconductor element electrically connected to a conductor provided on the board, a flexible printed circuit board connected to the SiC semiconductor element, are provided, the flexible printed circuit board has a conductor layer electrically connected to the SiC semiconductor element, the flexible printed circuit board is the flexible printed circuit board according to the above-described embodiment, it can be used as a power module. An example of this power module is shown in FIG. 2.

[0058] Referring to FIG. 2, an example of the power module 200 will be described. The power module 200 includes a resin case 310 and a heat sink 320 for releasing heat inside the module. The power module 200 also includes a DBC substrate 400, a plurality of SiC semiconductor elements 500 fixed to the DBC substrate 400, and a flexible printed circuit board (hereinafter referred to as "FPC100") according to the above-described embodiment. Although two SiC semiconductor elements 500 are provided in the figure, the number of SiC semiconductor elements is not limited. In FIG. 2, the depiction of the conductor forming the circuit pattern is omitted.

[0059] The DBC substrate 400 includes an insulating base material 410, and a first conductor layer 421 and a second conductor layer 422 provided on both surfaces of the base material 410, respectively. The base material 410 is made of a ceramic material or the like. The first conductor layer 421 is connected to and fixed to the heat sink 320. An external connection terminal 430 for electrically connecting to an external device is electrically connected to the second conductor layer 422.

[0060] The plurality of SiC semiconductor elements 500 are electrically connected to the second conductor layer 422 by a joining member 511 made of sintered silver, solder, or the like.

[0061] The FPC100 has an adhesive layer 120, a nickel-containing layer 130, and a conductor 140 laminated in this order on one surface of the base material layer 110, and an adhesive layer 122, a nickel-containing layer 132, and a conductor 141 laminated in this order on the other surface.

[0062] The conductor 140 is electrically connected to the SiC semiconductor element 500 by a joining member 512 made of sintered silver, solder, or the like. The conductor 140 is also electrically connected to the second conductor layer 422 in the DBC substrate 400 by a joining member 600 made of sintered silver, solder, or the like. Between each conductor layer, electrical connection can be made by through-holes, via holes, or the like according to the desired electrical circuit.

[0063] Further, the average thickness of the conductor 140, which is electrically connected to the SiC semiconductor element 500 and is the element-side conductor layer closest to the side where the SiC semiconductor element 500 is disposed, is configured to be 70 μm or more and 500 μm or less. Similarly, the average thickness of the conductor 141 is also configured to be 70 μm or more and 500 μm or less. Note that the conductor 141 can also be electrically connected to the SiC semiconductor element 500 via the conductor 140 and a through hole or via hole.

[0064] Furthermore, the FPC 100 has heat resistance such that the conductor 140, which is the element-side conductor layer, does not peel off from the base material layer 110 when 3000 hours have elapsed in an environment of 225°C. Also, the FPC 100 has heat resistance such that the conductor 140 does not peel off from the coating layer when 3000 hours have elapsed in an environment of 225°C. Here, the coating layer is an element-side film provided via an adhesive layer on the side where the SiC semiconductor element 500 is disposed rather than the conductor 140 as the element-side conductor layer. Note that in the FPC 100, all the films and adhesive layers have heat resistance such that the film does not peel off from the conductor layer when 3000 hours have elapsed in an environment of 225°C.

[0065] Also, inside the case 310, a resin material 330, which is configured by curing after filling, is provided such that the DBC substrate 400, a plurality of SiC semiconductor elements 500, the FPC 100, and a part of the external connection terminal 430 are buried.

[0066] In the power module 200, by adopting the FPC 100, the wiring path length can be shortened. That is, by arranging the FPC 100 along the surface of the DBC substrate 400 via a plurality of SiC semiconductor elements 500, the wiring path length can be shortened compared with the case of adopting the wire bonding method. Thereby, the parasitic inductance can be reduced and the surge voltage can be suppressed. In addition, by adopting the FPC 100 which inherently has flexibility, it can be arranged following a plurality of SiC semiconductor elements 500 on the surface of the DBC substrate 400. Therefore, the module can be miniaturized compared with the case of adopting a rigid substrate.

Example

[0067] Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not construed as being limited to the following examples.

[0068] <Fabrication of flexible printed circuit board> [Example 1] · Fluorine-containing rubber double bond modification (unsaturated modified product of a binary copolymer of vinylidene fluoride and hexafluoropropene (copolymerization ratio: vinylidene fluoride / hexafluoropropene = 8 / 2), Mooney viscosity (ML 1+10 (121 ° C)): 98, double bond content: 4% by mass) 100 parts by mass · Silica (fumed silica: Aerosil 200 (Nippon Aerosil Co., Ltd.)) 15 parts by mass · Epoxy resin (solid softening point 95 ° C) o-cresol novolak type epoxy resin (N695 (DIC Corporation)) 20 parts by mass · Amine compound (4,4'-methylenebis(2-ethyl-6-methylaniline): Curehard MED-J manufactured by Kumiai Chemical Industry Co., Ltd.) 5 parts by mass Using methyl ethyl ketone, it was dissolved so that the solid content became 30% by mass to obtain an adhesive composition containing a fluorine-containing rubber. The 3% by mass thermogravimetric reduction temperature of the obtained adhesive composition was 373 °C. The silica was dispersed using a bead mill. Also, the solution of the obtained adhesive composition was applied to a polyimide film (UPILEX-S polyimide film manufactured by Ube Industries, Ltd., thickness 25 μm) so that the average thickness after drying would be 25 μm, and then dried with a hot air dryer at 140°C for 3 minutes to obtain an adhesive film in a B-stage state (semi-cured state). The adhesive-coated surface of this adhesive film and a laminated sheet 1 (CF-T4M-HD manufactured by Fukuda Metal Co., Ltd., electrolytic copper foil, average thickness 35 μm, mass per unit area of nickel in the nickel alloy layer 150 mg / m 2 ) in which a nickel alloy layer was laminated on one surface of the copper foil were thermocompression bonded using a vacuum press laminator at 160°C, 3 MPa, and under reduced pressure for 30 seconds. Then, it was heat-cured at 160°C for 10 hours to obtain a sheet-like test sample (area in the plane direction: 100 cm 2 ). Using the obtained test sample, the following evaluation was conducted. The results are shown in Table 1. In addition, the mass per unit area of metal elements other than Ni contained in the nickel alloy layer in this example was Zn: 7 mg / m 2 , Cr: 7 mg / m 2 .

[0069] [Example 2] A flexible printed circuit board was obtained in the same manner as in Example 1 except that the mass per unit area of nickel in the nickel alloy layer was changed to 239 mg / m 2 . In addition, the mass per unit area of metal elements other than Ni contained in the nickel alloy layer in this example was Zn: 6 mg / m 2 , Cr: 6 mg / m 2 .

[0070] [Example 3] A flexible printed circuit board was obtained in the same manner as in Example 1 except that the laminated sheet 1 was changed to a laminated sheet 2 (RCF foil manufactured by Fukuda Metal Co., Ltd., rolled copper foil, average thickness 35 μm, mass per unit area of nickel in the nickel alloy layer 150 mg / m 2 ). In addition, the mass per unit area of metal elements other than Ni contained in the nickel alloy layer in this example was Zn: 7 mg / m 2 , Cr: 7 mg / m 2 .

[0071] [Comparative Example 1] A flexible printed circuit board was obtained in the same manner as in Example 1, except that the mass per unit area of nickel in the nickel alloy layer was changed to 63 mg / m 2 . In addition, the mass per unit area of metal elements other than Ni contained in the nickel alloy layer in this comparative example was Zn: 7 mg / m 2 , Cr: 7 mg / m 2 .

[0072] [Comparative Example 2] A flexible printed circuit board was obtained in the same manner as in Example 1, except that the laminated sheet 1 was changed to a laminated sheet 3 (BHY-82F-HA-V2 manufactured by JX Metals Co., Ltd., average thickness 35 μm, mass per unit area of nickel in the nickel alloy layer 70 mg / m 2 ). In addition, the mass per unit area of metal elements other than Ni contained in the nickel alloy layer in this comparative example was Co: 169 mg / m 2 , Zn: 39 mg / m 2 , Cr: 6 mg / m 2 .

[0073] [Comparative Example 3] A flexible printed circuit board was obtained in the same manner as in Example 3, except that the adhesive composition was changed to Epoxy AH357 manufactured by Printec Co., Ltd. At this time, the polyimide film was coated so that the average thickness after drying would be 25 μm. In addition, the mass per unit area of metal elements other than Ni contained in the nickel alloy layer in this comparative example was Zn: 7 mg / m 2 , Cr: 7 mg / m 2 .

[0074] [Comparative Example 4] A flexible printed circuit board was obtained in the same manner as in Example 1, except that the nickel-containing alloy layer of the laminated sheet 1 was changed to a nickel-free alloy layer, and the adhesive composition was changed to Epoxy AH357 manufactured by Printec Co., Ltd. At this time, the polyimide film was coated so that the average thickness after drying of the adhesive composition was 25 μm. Note that the mass per unit area of the metal elements contained in the nickel-free alloy layer in this comparative example was Co: 33 mg / m 2 , Mo: 26 mg / m 2 , Zn: 17 mg / m 2 , Cr: 12 mg / m 2 .

[0075] <Evaluation> [Nickel content] A first mixed solution mixed at a volume ratio of hydrochloric acid: nitric acid = 3:1 and a second mixed solution mixed at a volume ratio of water: aqua regia = 3:2 (mixed by adding aqua regia to water) were obtained. The laminated sheet 1, laminated sheet 2, or laminated sheet 3 was immersed in the second mixed solution for extraction, and ICP emission analysis was performed using the obtained extract to determine the amount of nickel. Finally, the mass per unit area of nickel in the nickel-containing layer was calculated by dividing the content of nickel in the nickel-containing layer by the area in the planar direction of the nickel-containing layer. The evaluation results are shown in Table 1.

[0076] The thickness of the nickel-containing layer was calculated from the mass per unit area of the metal elements contained in the nickel-containing layer and the specific gravity of each metal element. The calculated results are shown in Table 1.

[0077] [Peel strength] After storing at 225°C for the time shown in Table 1, the peel strength was evaluated in accordance with IPC TM650 2.4.9 (Free Wheeling Rotary Drum Method). Note that the initial (0-hour) peel strength is the peel strength evaluated before storage. At this time, three evaluation samples were prepared for evaluation, and the average value was adopted. The evaluation results are shown in Table 1.

[0078] [Oxygen Permeability Rate] The oxygen permeability rate of the polyimide film (UPILEX-S) was measured according to the following measurement conditions. The measurement results were 5.93×10 -14 cc·cm / cm 2 ·sec·cmHg at 25°C, 1.67×10 -12 cc·cm / cm 2 ·sec·cmHg at 120°C, and 8.72×10 -12 cc·cm / cm 2 ·sec·cmHg at 200°C. (Measurement Conditions for Oxygen Permeability Rate) Measurement method: Conforming to Appendix 2 of JIS K7126-1 Test gas type: Oxygen Test gas flow rate: 90 ml / min Carrier gas type: Helium Carrier gas flow rate: 35 ml / min Permeation area: 15.2 cm 2 Measuring device: GTR-30XANO (25°C, 120°C), GTR-10AH (200°C); both are manufactured by GTR Tech Cell thermostat temperature: 25°C, 120°C, 200°C Gas chromatograph calibration method: Two-point calibration with 0.0 μl and 15.3 μl

[0079]

Table 1

[0080] From the comparison between Comparative Examples 3 to 4 and other comparative examples and examples, it was found that by using an adhesive containing a fluorine-containing rubber, a flexible printed circuit board in which peeling of the adhesive layer hardly occurs even at a high temperature of 225°C can be obtained. Also, from the comparison between Examples 1 to 3 and Comparative Examples 1 to 2, the mass per unit area of nickel in the nickel-containing layer was 100 mg / m 2As described above, it has been found that a flexible printed circuit board in which peeling of the adhesive layer hardly occurs even in an environment of long-term high temperature of 225°C for 3000 hours can be obtained.

[0081] From the above, according to the present invention, it has been found that a flexible printed circuit board in which peeling of the adhesive layer hardly occurs even when held in an environment of high temperature for a long period can be provided as compared with a conventional flexible printed circuit board.

Explanation of Signs

[0082] 100 Flexible printed circuit board 110 Base material layer 120, 122 Adhesive layer 130, 132 Nickel-containing layer 140, 141 Conductor 200 Power module 310 Case 320 Heat sink 330 Resin material 400 DBC substrate 410 Base material 421 First conductor layer 422 Second conductor layer 430 External connection terminal 500 SiC semiconductor element 511, 512, 600 Joining member

Claims

1. having at least a base material layer, an adhesive layer, a nickel-containing layer, and a conductor, in this order, wherein the adhesive layer contains a fluorine-containing rubber, The mass per unit area of nickel in the nickel-containing layer is 100 mg / m ２ or more, the flexible printed circuit board.

2. The flexible printed circuit board according to claim 1, wherein the base material layer contains polyimide.

3. The mass per unit area of nickel in the nickel-containing layer is 125 mg / m ２ or more and 500 mg / m ２ or less. The flexible printed circuit board according to claim 1 or 2.

4. The flexible printed circuit board according to claim 1 or 2, wherein the conductor contains copper.

5. a lamination step of obtaining a laminate including at least a base material layer, an adhesive layer, a nickel-containing layer, and a conductor layer, in this order, and a circuit pattern forming step of processing the laminate so that a circuit pattern is formed, wherein the adhesive layer contains a fluorine-containing rubber, The mass per unit area of nickel in the nickel-containing layer is 100 mg / m ２ or more. A method for manufacturing a flexible printed circuit board.

6. The method for manufacturing a flexible printed circuit board according to claim 5, wherein the lamination step includes a step of bonding the base material layer and a laminate layer composed of the nickel-containing layer and the conductor layer with an adhesive.

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